Compositions and methods for promoting hair growth

ABSTRACT

The present invention provides compositions and methods for promoting hair growth. The methods generally comprise the administration to a patient of a therapeutically effective amount of the compositions of the present invention which employ a vasodilator in combination with estradiol and/or a 5-α-reductase inhibitor in a pharmaceutically acceptable vehicle. The compositions and methods of the present invention are suitable for the treatment of baldness, in particular, male pattern baldness.

This is a continuation patent application Ser. No. 08/020,202 filed Feb.19, 1993, now U.S. Pat. No. 5,407,944.

FIELD OF THE INVENTION

The present invention relates generally to compositions and methods forpromoting hair growth and, more particularly, to compositions andmethods for treatment for baldness. The compositions and methods of thepresent invention employ two or more agents selected from the groupconsisting of vasodilators, estradiols and/or 5-α-reductase inhibitors.

BACKGROUND OF THE INVENTION

Male pattern baldness (MPB) affects 60-80% of the male caucasianpopulation with advancing age. Anderson, R. D., Clin. Plast. Surg.1987:14,(3):447. Various etiologies for MPB have been proposed whichinclude age, genetic androgens and scalp tension. In particular, in 1942and 1951, it was reported that the etiology of MPB was related to aninterdependent relationship of age, genetic predisposition andandrogens. Hamilton, J. B., Am. J. Anat. 1942:71:451-480 and Hamilton,J. B. Ann NY Acad. Sci. 1951:53:708. It was found that MPB would notoccur unless androgens were present and that androgens would not induceMPB without genetic predisposition. In 1959 it was postulated that MPBwas linked to an androgen-sensitive, genetically pre-disposed senescenceof hair follicles. These genetically predisposed hair follicles werelocated in the frontal and crown regions of the scalp. This theory(sometimes called "Donor Dominance") has prevailed for over thirtyyears.

Most treatment modalities currently employed (such as hairtransplantation) have been performed based on this theory. However,transplantation methods are somewhat complex and no single treatmentmodality has proven completely or repeatably successful in inducing,maintaining and/or increasing hair growth.

More recently, in 1980, the reversal of MPB in a male patient receivingminoxidil for hypertension was revealed and minoxidil has since beenused to promote hair growth, most commonly by topical application.Zapacosta, A. R., N. Eng. J. Med. 1980:303:1480-1481. Minoxidil'svasodilating effect on the scalp is one of the proposed mechanisms bywhich minoxidil promotes hair growth. However, despite its popularity,minoxidil has not performed in a completely satisfactory fashion inpromoting hair growth in all target populations.

In summary, although various etiologies for baldness have been proposedand many treatments based on these etiologies attempted, the underlyingpathophysiologies which cause baldness have not been elucidated. It isclear that without the identification of such pathophysiologies, nosingle treatment could be developed.

It would thus be desirable to develop a predictable method for treatingbaldness including male pattern baldness by promoting hair growth. Itwould also be desirable to develop a method for promoting hair growthbased on the here-to-fore unrecognized pathophysiology which appears tocause baldness once identified.

SUMMARY OF THE INVENTION

The present invention provides compositions and methods for promotinghair growth.

The methods of the present invention generally comprise the treatment ofa patient (in need of such treatment) with a therapeutically-effectiveamount of a vasodilator in combination with either an estradiol; or a5-α-reductase inhibitor or a mixture of all three, preferably for a timesufficient to promote sufficient hair growth. The methods preferablyinclude administration of the selected agents from apharmaceutically-acceptable vehicle; however, the agents can beconcomitantly administered via different modes, e.g., a combination oftopical, oral, etc. The methods of the present invention are suitablefor the treatment of baldness and, in particular, male pattern baldness.

The compositions of the present invention comprise mixtures of theseagents, (a vasodilator plus an estradiol or a 5-α-reductase inhibitor;or a mixture of all three) preferably in a topical or oral unit dosageform.

A better understanding of the present invention and its advantages willbe had from a reading of the Detailed Description of the PreferredEmbodiments taken in combination with the Drawings and Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The various advantages of the present invention will become apparent toone skilled in the art by reading the following specification andsubjoined claims and by referencing the following drawings in which:

FIG. 1 is a sample plot illustrating the PtcO₂ (mm Hg) versus time of acontrol subject following release of a scalp tourniquet;

FIG. 2 is a bar graph illustrating the frontal and temporal scalptemperature of bald and control subjects;

FIG. 3 is a bar graph illustrating the maximum initial slopes (dPtcO₂/dt [mm Hg/min]) of the frontal and temporal scalps of bald and controlsubjects; and

FIG. 4 is a bar graph illustrating the resting transcutaneous PO₂ of thefrontal and temporal scalps of bald and control subjects.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to compositions and methods for promotinghair growth. In accordance with the present invention, a therapeuticallyeffective amount of a mixture of agents, preferably comprising avasodilator in combination with an estradiol and/or a 5-α-reductaseinhibitor, is formulated and administered to a patient to promote hairgrowth. The method of the present invention finds use in any patient(human or other mammal) seeking to induce, maintain or increase hairgrowth. The method of the present invention is suitable for thetreatment of various types of baldness, in particular, male patternbaldness (MPB) or alopecia.

While not intending to be based by theory, it is believed that localtissue hypoxia may be the underlying pathophysiology by which age,genetics and androgens interact to cause baldness. The method of thepresent invention is based on the recognition of this underlyingbaldness-inducing pathophysiology.

It should be appreciated that while this invention preferablycontemplates topical or oral administration, nothing herein should beconstrued to limit the mode of delivery. Both topical and systemicroutes of delivery may be appropriate, particularly incombination-therapy regimes.

Further, it should also be appreciated that each agent of thecombination need not be administered in the same manner, i.e., one ormore may be administered topically while another may be administeredsystemically. It therefore follows that while the agents selected forthe methods of the present invention are preferably administeredconcomitantly, the administration need not be coinstantaneously. It ispreferred that they be administered to such that their therapeuticaleffects are synchronized or overlap. Based upon ease of treatment,however, in a highly preferred embodiment the selected agents areadministered from a single vehicle in unit dosage form, includingtablet, capsule, and transdermal patches or preparation.

It will be appreciated that the actives useful in the compositions andmethods of the present invention may also be employed inpharmaceutically-acceptable forms such as esters, salts, or aspro-drugs.

In practicing the method of the present invention, the amount ofvasodilator, estradiol and 5-α-reductase inhibitor to be administered(as well as other factors in the treatment regime) will vary with thepatient being treated and will be monitored on a patient-by-patientbasis by the physician or other health-care provider. Generally, atherapeutically-effective amount of the compounds of the presentinvention will be applied for a therapeutically effective duration. By"therapeutically-effective amount" and "therapeutically-effectiveduration" is preferably meant an amount or duration effective to achievea selected desired result In accordance with the present inventionwithout undue adverse physiological effects or side effects; the desiredresult generally being a clinically observable increase in hair growthat the target situs.

Without limitation, it is contemplated that the vasodilators useful inthe present invention may operate by any mechanism of action and maypreferably be selected from the group consisting of minoxidil,nitroglycerin, diazoxide, or mixtures thereof. Calcium ion influxinhibitors (calcium channel blockers) such as nifedipine, are alsocontemplated as preferred vasodilators in the present invention.

Minoxidil is chemically described as2,4-pyrimidinediamine,6-(1-piperidinyl)-,3-oxide and has a molecularweight of 209.25. It is contemplated that minoxidil will be effectivewhen delivered in a topical composition comprising from about 0.01% toabout 5% minoxidil and by oral administration in the range of from about5 to about 100 mg dose per day. A highly preferred topical vasodilatorcomposition is a minoxidil-containing preparation marketed by The UpjohnCompany under the registered trademark Rogaine. Rogaine topical solutionis available at a concentration of 2% in a solution of (60% v/v)propylene glycol, and water. The preferred dosage of Rogaine solution isabout 2 mL per day.

Minoxidil in tablet form (likewise marketed by Upjohn) under thetradename Loniten, is another highly preferred vasodilator. Lonitentablets typically contain from about 2.5 mg to about 10 mg of minoxidilas well as the following inactive ingredients: cellulose, corn starch,lactose, magnesium stearate and silicon dioxide. The preferred dosage ofminoxidil is from about 1 to about 300 mg per day. The more preferreddosage is from about 5 to about 100 mg per day. The most preferreddosage is from about 10 to about 40 mg per day.

Another highly preferred vasodilator for use in the compositions andmethods of the present invention is nitroglycerin, available fromvarious companies in various forms, i.e. transdermal systems, ointments,oral tablets, sprays, and other delivery forms. Nitroglycerin ischemically described as 1,2,3-propanetriol trinitrate and has amolecular weight of 227.09. A preferred transdermal system is marketedunder the trademark Nitro-Dur by Key Pharmaceuticals, Inc. Thecomposition and use of Nitro-Dur is discussed at pages 1191-1192 of thePhysicians Desk Reference, 47th ed. (1993) which Applicants hereinincorporate by reference.

Another highly preferred vasodilator for use in the compositions andmethods of the present invention is diazoxide, marketed by Baker NortonPharmaceuticals, Inc. under the trademark Proglycem. Diazoxide ischemically described as7-chloro-3-methyl-2H-1,2,4-benzothiadiazine1,1-diazoxide. Proglycem isavailable for oral administration in capsule or suspension form. Thepreferred dosage of diazoxide is from about 1 to about 24 mg/kg per day.The more preferred dosage is from about 1 to about 16 mg/kg per day. Themost preferred dosage is from about 3 to about 8 mg/kg per day.

Another highly preferred vasodilator is nifedipine, marketed by PfizerLabs under the trademark Procardia. Nifedipine is an antianginal drugbelonging to a class of pharmacological agents known as calcium channelblockers. Nifedipine is chemically described as 3,5-pyridinedicarboxylicacid,1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl),-dimethyl ester. It hasan empirical formula represented by C₁₇ H₁₈ N₂ O₆ and a molecular weightof 346.3. Procardia is typically employed in capsule form containing 10mg to 20 mg nifedipine per capsule. Inert ingredients in theformulations include: glycerin; peppermint oil; polyethylene glycol;soft gelatin capsules (which contain Yellow 6, and may contain RedFerric Oxide and other inert ingredients), and water. The 10 mg capsulesalso contain saccharin sodium, The preferred dosage of Procardia(nifedipine) is from about 10 to about 120 mg per day. The morepreferred dosage is from about 20 to about 100 mg per day. The mostpreferred dosage is from about 30 to about 60 mg per day.

Other actives in the class of calcium channel blockers are alsocontemplated as preferred vasodilators in the present invention.

Procardia XL is the trademark for nifedipine GITS (GastrointestinalTherapeutic System) and is also available through Pfizer Labs. ProcardiaXL is a tablet formulated as a once-a-day controlled release tablet fororal administration designed to deliver 30, 60 or 90 mg of nifedipineper tablet. Inert ingredients in the formulations include: celluloseacetate; hydroxypropyl cellulose; hydroxypropyl methylcellulose;magnesium stearate; polyethylene glycol; polyethylene oxide; red ferricoxide; sodium chloride and titanium dioxide. A preferred dosage ofProcardia XL (nifedipine GITS) is from about 10 to about 90 mg per day.A more preferred dosage of Procardia XL is from about 20 to about 80 mgper day. A highly preferred dosage of Procardia XL is from about 30 toabout 60 mg per day.

A highly preferred estradiol for use in the compositions and methods ofthe present invention include 17 β-estradiol, marketed by Mead JohnsonLaboratories under the trademark Estrace. Estradiol is believed to bethe most potent physiologic estrogen and is the major endogenousestrogenic hormone. 17 β-estradiol is chemically described asestra-1,3,5(10)-triene-3,17 β-diol. Estrace is commercially available intablet or cream form. The estradiol in Estrace tablets has beenmicronized and is rapidly and effectively absorbed from thegastrointestinal tract according to Mead. Estrace tablets which contain1 mg of estradiol also contain the following inactive ingredients:acacia, D&C Red No. 27 (aluminum lake), dibasic calcium phosphate, FD&CBlue No. 1 (aluminum lake), lactose, magnesium stearate, colloidalsilicon dioxide, starch (corn) and talc. Estrace tablets which contain 2mg of estradiol also contain the following inactive ingredients: acacia,dibasic calcium phosphate, FD&C Blue No. 1 (aluminum lake), FD&C YellowNo. 5 (tartrazine) (aluminum lake), lactose, magnesium stearate,colloidal silicon dioxide, starch (corn) and talc. Each gram of Estracein cream form contains 0.1 mg estradiol in a nonliquefying basecontaining purified water, propylene glycol, stearyl alcohol, whiteceresin wax, glyceryl monostearate, hydroxypropyl methylcellulose, 22084000 cps, sodium lauryl sulfate, methylparaben, edetate disodium andtertiary-butylhydroquinone.

The preferred dosage of estradiol in tablet form is from about 1 toabout 90 mg micronized estradiol per day. A more preferred dosage isfrom about 1 to about 60 mg micronized estradiol per day. A highlypreferred dosage is from about 1 to about 30 mg micronized estradiol perday. A preferred dosage of Estrace in cream form is from about 1 toabout 12 g (about 0.1 to about 1.2 mg estradiol) per day. A morepreferred dosage is from about 1.5 to about 8 g (about 0.15 to about 0.8mg estradiol) per day. A highly preferred dosage is from about 2 toabout 4 g (about 0.2 to about 0.4 mg estradiol) per day.

Another highly preferred estradiol is an estradiol transdermal systemmarketed by CIBA Pharmaceutical Company under the registered trademarkEstraderm. Estraderm is designed to release 17 β-estradiol through arate limiting membrane continuously upon application to intact skin.Estraderm is available in two dosage systems, to provide nominal in vivodelivery of 0.05 or 0.1 mg of estradiol per day via skin of averagepermeability. The system providing 0.05 mg of estradiol per day has acontact surface of 10 cm², contains 4 mg of estradiol USP and 0.3 ml ofalcohol USP. The system providing 0.1 mg of estradiol per day has acontact surface area of 20 cm², contains 4 mg of estradiol USP and 0.6ml of alcohol USP.

A highly preferred inhibitor of the steroid 5-α-reductase for use in thecompositions and methods of the present invention, is a synthetic4-azasteroid compound marketed by Merck & Co., Inc. under the registeredtrademark Proscar; this active is also called finasteride. Finasterideis 4-azaandrost-1-ene-17-carboxamide, N-(1,1-dimethylethyl)-3-oxo-,(5α,17β)-. It has an empirical formula represented by C₂₃ H₃₆ N₂ O₂ and amolecular weight of 372.55. Proscar tablets contain 5 mg of finasterideas well as the following inactives: docusate sodium, FD&C Blue2(aluminum lake), hydrous lactose, hydroxypropyl cellulose LF,hydroxypropylmethyl cellulose, magnesium stearate, microcrystallinecellulose, pregelatinized starch, purified water, sodium starchglycolate, talc, titanium dioxide and yellow iron oxide. The preferreddosage of Proscar (finasteride) is from about 0.5 to about 15 mg perday. The more preferred dosage is from about 3 to about 10 mg per day.The most preferred dosage is from about 4 to about 6 mg per day.

It should be appreciated that duration of treatment according to themethods of the present invention will vary with many factors and willprimarily depend upon the specific condition of the patient, the targetsitus, and the specific combination of agents employed. It should alsobe appreciated that both treatment agents, dosage and duration will beinterdependent and can be varied together in order to achieve an optimalclinical response. In addition, dosage and duration will also depend onthe specific combination of agents employed.

The agents utilized in the compositions and methods of the presentinvention can be administered in accordance with the present inventionin any pharmaceutically-acceptable carrier, preferably one which is bothnon-toxic and suitable for topical or systemic delivery. The compoundsmay be formulated for administration by procedures well-established inthe pharmaceutical arts.

For topical administration, pharmaceutically-acceptable vehicles in theform of creams, oils, ointments, gels, pastes, liquids, powders, sprays,dips, transdermal patches, and other delivery modes known to thoseskilled in the art may be utilized. A topical vehicle or vehiclecomponent is generally "pharmaceutically-acceptable" if the vehicle orcomponent does not substantially interfere with the pharmacologicalactivity of the agent or agents and does not cause undue side effects.

The agents may also be employed in unit dosage forms. These can compriseabout 1 to about 500 mg of vasodilator; about 1 to about 150 mg ofestradiol, and/or about 0.1 to about 50 mg of 5-α-reductase inhibitor.

For example, a pharmaceutical preparation in unit dosage form adaptedfor administration to promote hair growth may be prepared comprising,per unit dosage, at least two active agents selected from the groupconsisting of minoxidil, estradiol and finasteride each in an effectivenon-toxic amount within the range of from about 1 to about 300 mgminoxidil; about 1 to about 90 mg estradiol; and about 0.5 to about 15mg finasteride.

Such unit dosage preparations may be adapted for oral administration asa tablet, capsule, liquid, powder, bolus or the like. They may likewisebe prepared in unit dosage form in an ingestible or injectable ortopical form.

Art-disclosed formulation ingredients such as tableting agents,colorants, flavorants, anti-oxidants, emollients, surface-active agents,encapsulation agents, and the like may also be employed.

All percentages (%) herein are percentages by weight unless otherwiseindicated or apparent from the context of use. The term "comprising" asused herein includes the more limiting terms of "consisting essentiallyof" and "consisting of."

The following Examples and Discussion of Results further describe thecompositions and methods of the present invention.

EXAMPLE 1

A study was performed to determine if there is a relative microvascularinsufficiency and associated tissue hypoxia to regions of bald scalp inmen with male pattern baldness as compared to hair bearing scalp in menwith no baldness.

Eighteen male volunteers (age ≧18 years old), all of which werenon-smokers, were used in the study. Nine of the men had MPB, witheither Juri degree II or Ill (fronto-parietal or fronto-parietal-crownbaldness). Juri, J. et al., Clin. Plast. Surg. 1982:9:255. Nine of themen were controls, with no MPB. Both groups had similar mean ages, themean age of the bald subjects was 33.8 years ±2.3; while the mean age ofthe control subjects was 28.6 years ±0.6. All measurements were obtainedwhile the subjects were seated with an ambient temperature of about25-30 degrees centigrade.

Frontal and temporal measurement sites were used in each subject. Toconsistently place the frontal site, a nasion to occipital protuberancedistance was obtained in all subjects. The frontal site was then placedat 31% of the nasion to occipital protuberance distance in the midline,as measured from the nasion. This distance placed the measurement sitewell behind the hair line in all of the controls. The temporal site wasplaced in the left temporal hair bearing region immediately superior tothe helix of the left ear. A First Temp Thermometer (Intelligent MedicalSystems Inc., Carlsbad, Calif.) was used to measure the surfacetemperature at each site in each subject. A 1.5 cm diameter circle wasshaved at each site in all subjects (villus hair was shaved in thefrontal region of the bald subjects). Sites were cleansed with analcohol pad, and a transcutaneous PO₂ sensor (SensorMedics Corp., Yorba,Calif.) was placed at each site. Sensors were affixed to the skin withdouble-sided adhesive rings and a small drop of sterile H₂ O as thecontact medium. The sensor characteristics included a 90% response time(T₉₀) of 12 seconds, and an accuracy of ±3 mm Hg a 90 mm HgO₂. Eachtranscutaneous PO₂ monitor was calibrated on the same base station priorto use on each subject. The sensors were set at an operating temperatureof 43 degrees centigrade.

Resting PtcO₂ was obtained at each site. A scalp tourniquet was thenapplied until the PtcO₂ decreased to<2 mm Hg (±2 mm Hg). Temporal scalppressure was applied as needed to produce ischemia of the entire scalp.The tourniquet was released and PtcO₂ readings were obtained every 6seconds providing a sufficient number of data points within the T₉₀ ofthe transcutaneous PO₂ monitor. Data was analyzed by Repeated MeasuresAnalysis of Variance, with significance assessed at p<.05. A BLSD testwas then performed to determine differences between individual means,with significance assessed at p<.05. (Data is presented as mean±standard error in mean (SEM)).

The advantage of using the transcutaneous PO₂ (PtcO₂) method forevaluating the circulation of the scalp is that it is non-invasive andprovides a direct measure of the tissue (dermal) PO₂ surrounding thehair follicles. In addition, by placing a probe in the frontal andtemporal regions of the scalp, bald and hair bearing scalp in the sameMPB subject was compared to control subjects. Also, studies have shownthat the transcutaneous PO₂ can be used to assess the state ofperipheral circulation. This is based on the principle that a regionwith insufficient peripheral blood flow will have a prolongedpost-occlusive PtcO₂ recovery time. Lemke, R. et al., Critical CareMedicine 1988:16(4):353-357 and Kram, H. B. et al., J. Vasc. Surg.1984:1 (5):628-834. In turn, post occlusive maximum initial slope(dPtcO₂ /dt) should be proportional to the blood flow of a given regionof scalp.

PtcO₂ versus time was plotted for each site, a tangent to the steepestportion of the curve was drawn, and a maximum initial slope calculated.FIG. 1 depicts a sample plot of PtcO₂ (mm Hg) versus time (sec) from thetemporal region of a control subject following release of the scalptourniquet. The shaded line in FIG. 1 represents the steepest initialportion of the curve used for slope calculations. All graphing and slopecalculations were performed by computer, using a Cricket graph 2.0program on a Macintosh IIci.

Scalp temperatures were also recorded in order to determine if there wasa difference in temperature between bald scalp and hair bearing scalp inthe bald subjects compared to controls. As shown in FIG. 2, the temporalscalp temperature was statistically significantly higher (approximately1° F. (0.6°-1.1° F.)) than frontal scalp temperature in both baldsubjects and controls. However, there was no significant difference inscalp temperatures between bald subjects and controls. Thus, anydifferences in scalp blood flow and PtcO₂ observed between bald subjectsand controls can not be attributed to differences in scalp temperature.

FIG. 3 illustrates the maximum initial slopes (dPtcO₂ /dt [mm Hg/min])of the frontal and temporal scalps of the nine bald and nine controlsubjects. Slopes were calculated from the initial steepest portion ofthe post occlusive PtcO₂ versus time for each scalp region in eachsubject. Scalp blood flow, which is proportional to maximum initialslope (d PtcO₂ /dt), was significantly lower in the bald subjectsrelative to controls. Comparing individual slopes reveals that in thebald subjects the frontal (non-hair bearing region) blood flow(30.3±3.93) was significantly less than the temporal (hair bearingregion) blood flow (66.8±5.40). In control patients, there was nosignificant difference between the frontal blood flow (56.3±9.32) andthe temporal blood flow (79.2±8.94). Although comparing the frontalblood flow in the bald and control patients did not yield a significantdifference (p>.05), the bald frontal slope was 54% lower than that ofthe controls.

FIG. 4 represents the resting transcutaneous PO₂ (PtcO₂ mm Hg) of thefrontal and temporal scalps of the nine bald subjects and nine controls.As shown, resting transcutaneous PO₂ (PtcO₂) was significantly lower inbald frontal scalp (32.2 mm Hg±2.0) than hair bearing temporal scalp(51.8 mm Hg±4.4) in men with MPB. In controls, there was nostatistically significant difference in PtcO₂ of frontal scalp (53.9 mmHg±3.5) and temporal scalp (61.4 mm Hg±2.7). Further, in bald subjectsthe frontal scalp PtcO₂ was also significantly lower (32.2 mm Hg±2.0)than in either frontal or temporal scalp of the controls (53.9 mm Hg±3.5& 61.4 mm Hg±2.7, respectively). Finally, the PtcO₂ of the temporalscalps was not significantly different between bald and control subjects(51.8 mm Hg±4.4 & 61.4 mm Hg±2.7, respectively).

Overall, scalp blood flow of control subjects was significantly greaterthan that of MPB subjects. Klemp et al., using a Xenon washouttechnique, also found that subcutaneous blood flow to normal scalps wasgreater than that of MPB patients. In addition, the present study wasalso able to document that the temporal blood flow is significantlygreater than the frontal blood flow in MPB subjects; while in controlsubjects there was no significant difference between frontal andtemporal regions. Also, there was no significant difference betweenblood flow to the temporal regions in MPB subjects and controls.Finally, a previously unknown local tissue hypoxia in bald scalpcompared to hair bearing scalp was identified.

EXAMPLE 2

In order to study the effectiveness of the compounds of the presentinvention, a prospective double blind study is performed. Men with earlymale pattern baldness are randomized to one of four groups. The firstgroup of subjects are treated with a topical preparation consisting of avasodilator only (i.e. minoxidil, nitroglycerin, diazoxide, nifedipine).The second group are treated with a mixture of a vasodilator plusestradiol. The third group are treated with a mixture of a vasodilator,estradiol, and a 5-α-reductase inhibitor (i.e. finasteride). The fourthgroup are controls, treated with carrier only (no actives). A fifthgroup is treated with a mixture of a vasodilator and a 5-α-reductaseinhibitor. Hair growth is measured at fixed intervals of time, based onstandard protocols. Analysis of variance, with significance assessed atp<.05 is used to identify statistically significant differences betweenthe treatment groups.

DISCUSSION OF RESULTS

Due to anatomical considerations, there is a relative microvascularinsufficiency to regions of the scalp that lose hair in MPB. The scalpis not avascular in bald subjects; however, there is a relativemicrovascular insufficiency to those regions that lose hair compared tothose that do not, and this results in a relative local tissue hypoxiabelow the level needed for hair growth. The following suggests that alocal tissue hypoxia may be the underlying pathophysiology by which age,genetics, and androgens interact to cause MPB. Thus, improving localtissue PO₂ of the frontal and crown scalp may be a prerequisite topreventing or reversing early MPB. This might be accomplished medicallyor surgically. However, a combined treatment of vasodilator, estradioland/or a 5-α-reductase inhibitor presently represents the optimummedical treatment for early MPB.

Anatomy. Due to the underlying anatomy, there is a relativemicrovascular insufficiency to regions of the scalp which lose hair inMPB, which is associated with a local tissue hypoxia in those regions.The vascular supply of the scalp is derived from branches of theinternal carotid artery and branches of the external carotid artery.Dingman, R. O. et al., Clin. Plast. Surg. 1982:9:131. The frontal regionof the scalp, which loses hair in MPB, is primarily supplied by thesupraorbital and the supratrochlear arteries. These are relatively smallbranches of the internal carotid artery system. The temporal andoccipital regions of the scalp, which do not lose hair in MPB, aresupplied by larger branches of the external carotid artery.Specifically, these are the superficial temporal, posterior auricular,and occipital arteries. Further, the frontal and vertex regions of thescalp overly the galea aponeurotica, which is relatively avascular. Thetemporal and occipital regions of the scalp overly the temporalis andoccipitalis muscles, which provide a rich network of musculocutaneousperforator blood vessels. These anatomical differences contribute to thetenuous nature of the dermal blood supply to the frontal and crownregions of the scalp.

One of the early manifestations of vascular insufficiency of the lowerextremities is hair loss. The mechanism by which vascular insufficiencycauses hair loss is not known. However, Hunt and Pai showed thatcollagen syntheses by fibroblasts is significantly compromised whentissue PO₂ <40 mm Hg. Hunt T. K. et al., Surg. Gynecol. Obstet.1972:135:351. There may be an analogous situation with keratinproduction by hair follicle cells.

Keratin Synthesis. The normal scalp has roughly 100,000 hairs, with a2-6 year anagen phase (growth phase) and roughly a 3 month telogen phase(rest phase). Hair fiber formation is a dynamic process which requirescell proliferation, cell movement, and cell migration. Marshall, R. C.et al., Microsc. 1991 :Rev, Vol. 4(1):47-83. Human hair is made up ofhard α-keratin, a protein which is rich in the amino acid cysteine(10-14% cysteine). Lehninger, A. L., Biochemistry, 3rd ed; 1988:126-135.Keratin, like collagen, is composed of multistrand structures in whichpeptide chains arranged in an α-helix are wound around each other in atertiary super coil structure and stabilized by covalent cross links.Devlin, T. M. Textbook of Biochemistry with Clinical Correlations. 3rded. 1991:66-67. It has been shown that the mechanical strength, elasticproperty and biological resistance of keratins stem directly from thethree dimensional structure stabilized by the formation of disulfidebonds. The stabilization of keratin involves the oxidation of cysteinesulfhydryl residues to give cysteine disulfide bonds, primarily betweenprotein chains. The formation of these disulfide cross links lead to theproduction of a mature hair fiber.

Thus, the stabilization of the tertiary structure of keratin andultimate maturation of the hair fiber depends on the oxidative formationof disulfide bonds. This oxidative reaction likely requires oxygen. Asdescribed in Example 1, there is a local tissue hypoxia to regions ofthe scalp that lose hair in MPB. This local tissue hypoxia may result indecreased mature keratin production and thus manifest as diminished hairfiber formation. Hunt and Pai, supra, have found that in a hypoxicenvironment collagen synthesis is significantly decreased. Studies havealso shown that prolyl-4-hydroxylase, the enzyme which hydroxylatesproline and ultimately allows for the cross linking and stabilization ofcollagen, has a K_(m) (O₂) of approximately 20-25 mm Hg. Jonsson, K. etal., Ann Surg. 1991:314(5):605-613. That is, at a tissue PO₂ of 20-25 mmHg, the enzyme is only operating at 50% of maximal velocity. In thesubjects of the study described in Example 1, with MPB, the bald frontalscalp had a PtcO₂ of 32.2 mm Hg.

It is not yet clear which critical enzyme in keratin disulfide bondformation is affected in an hypoxic environment. However, Buxman hasproposed that γ-glutamyl transpeptidase may be the enzyme involved inthe disulfide crosslinking of keratin. Histochemically, the enzyme islocalized to the keratinizing region of the hair follicle and is onlypresent during anagen phase. Buxman, M. M. Int. J. Dermatol.1981:20(2):95-98. γ-Glutamyl transpeptidase may be the key point atwhich hypoxia interferes with mature cross-linked α-keratin and hairfiber formation. Given the inherent similarity between collagen andkeratin, it is reasonable to presume that the inability to form covalentcross links in a hypoxic environment will result in decreased keratindeposition similar to that found with collagen. Decreased keratindeposition would result in decreased hair growth just as decreased woundhealing was seen by Hunt and Pai when collagen deposition was decreased.

Androgens. Androgens are also involved in the development of MPB. Theandrogenetic theory to date as expressed by Orentreich, implies that thehair follicles in the crown and frontal regions are geneticallydifferent than those located in the temporal and occipital regions. Inturn, with androgen stimulation, these genetically predisposed hairfollicles become senescent.

In males, the majority of testosterone is synthesized in the testis. Therate limiting step in the production of testerone is the conversion ofcholesterol to pregnenolone by the γ⁵ pathway. This rate-limiting steprequires NADPH and O₂, both of which should be abundant in the testis.Testosterone is then peripherally converted to two active metabolites,dihydrotestosterone and estradiol. Studies have documented thatdihydrotestosterone (DHT) is the tissue active androgen and the cellularmediator of androgen action. Bruchovsky, N. et al., J. Biol. Chem.1968:243:2012, Fang. S. et al., J. Biol Chem. 1969:244:6584 and WilsonJ. D. et al., Williams Textbook of Endocrinology. 8th ed. 1992:805-809.The DHT-receptor complex is responsible for external virilization anddevelopment of most male secondary sex characteristics. The conversionof testosterone to DHT requires the enzyme reductase activity (as wellas NADPH). Takayasu, S. et al., JCE&M 1972:34(6):1098-1101. Estradiolproduction from testosterone also occurs in the periphery and recentimmunohistochemical studies have revealed that the aromatase enzyme ispresent in hair follicles, with accentuated staining during anagenphase. Sawaya, M. E et al, J. Cutaneous. Pathol. 1992:19(4):309-314. Thearomatization of testosterone requires hydroxylation and oxidation.

Testosterone synthesis in MPB subjects should not be affected by scalphypoxia, since the majority of testosterone in males is produced in thetestis. In the hypoxic environment of the bald scalp, DHT synthesisshould not be significantly impaired. Schweikert and Wilson havedocumented that 5-α-reduction of testosterone to DHT was increased inhair roots from the frontal scalps of balding individuals as compared toother hair bearing scalp sites in the same individuals or to frontalhair roots from women and non-balding men. Schweikert, H. U. et al.,JCE&M 1974:38(5):811-89. Estradiol synthesis, however, should bestoichiometrically decreased in a hypoxic environment. Three moles ofoxygen are required to convert one mole of testosterone to one mole ofestradiol. In a hypoxic region, the ratio of DHT to estradiol(DHT/estradiol) should be increased. Sawaya has shown that men with MPBhave nearly a two fold increase in 5-α-reductase activity of hairfollicles in balding frontal scalp, than in hair bearing occipitalscalp. However, hair follicles in the frontal region had nearly threetimes less aromatase activity than hair follicles in the occipitalregion in men with MPB. Sawaya, M. E. Ann. N.Y. Acad. Sci.1991:642:376-383. Finding that the DHT/estradiol ratio is elevated inbald scalp as compared to hair bearing scalp in MPB subjects, isconsistent with what would be expected in a hypoxic tissue environment.

If one were to develop a gradual local tissue hypoxia of the frontalscalp, the DHT/estradiol ratio might increase locally to a criticallevel at which point receptor hormone interactions might result in downregulation or inhibition of hair follicle cell function. In turn, thismight result in the ultimate conversion of terminal hair to villus hair,and the development of MPB. This inhibition may take the form ofaltering the number of hair follicle cells in anagen phase as comparedto telogen phase.

Orfanos and Vogels, in a controlled, randomized, double blind study,found that application of .025% estradiol for 6 months in subjects withMPB results in a decrease in the number of telogen hairs in 63% of thosetreated. A similar reduction was found in only 37% of the controls. Noregrowth of new hair was found in either group. Orfanos. C. E., et al.,Dermatologica 1980:161(2):124-132. The addition of estradiol to baldscalp would serve to locally decrease the DHT/estradiol ratio, Thisappears to decrease the number of hair follicles in resting phase.However, the delivery of adequate O₂ would be required to achievekeratin synthesis and hair growth. Thus, it is not surprising that hairregrowth did not occur with the addition of estradiol alone to baldscalps, without concomitant measures to correct the local tissuehypoxia.

Hair Follicle Genetics. In contrast to the "Donor Dominance" theory,hair follicles in the frontal and crown regions of the scalp may not begenetically different from those in the temporal and occipital regions.Rather, a local tissue hypoxia may alter the local hormonal milieu,specifically the DHT/estradiol ratio, and thus account for the androgenstimulated difference in hair production in these regions in MPBsubjects.

The clinical observation of progressive lower extremity hair loss inpatients with peripheral vascular disease of the lower extremitiesfavors a tissue hypoxia theory. A donor dominance theory for hair lossin this clinical scenario, would imply that the hair follicles in thetibial region are genetically predisposed to lose hair while those inthe thigh region are not in patients with distal lower extremityvascular disease. In Orentreich's original experiment (1959), bald scalptransplanted to hair-bearing scalp did not grow. This may have occurredbecause the hair follicles in the bald scalp were irreversibly atrophicfrom chronic hypoxia. The fact that autografts from hair bearing scalpgrew hair when transplanted to bald scalp appears to be contradictory.However, when transplanting hair bearing autografts, an incision is madein the scalp at the recipient site. This adds the confounding variableof neovascularization in that region. This neovascularization mayprovide sufficient O₂ to allow the local hormonal milieu to bepermissive for hair growth.

Hamilton has clearly documented that genetics play an important role inMPB. However, its role may be more specifically related to the geneticpredisposition for a particular vascular anatomy or the predispositionfor small vessel disease, than to differences between individual hairfollicles.

Those skilled in the art can now appreciate from the foregoingdescription that the broad teachings of the present invention can beimplemented in a variety of forms. Therefore, while this invention hasbeen described in connection with particular examples thereof, the truescope of the invention should not be so limited since othermodifications will become apparent to the skilled practitioner upon astudy of the specification and following claims.

What is claimed is:
 1. A pharmaceutical preparation in unit dosage formadapted for administration to promote hair growth comprising, per dosageunit, at least two active agents selected from the group consisting ofnitroglycerin, estradiol and finasteride in an effective nontoxicamount.
 2. The pharmaceutical preparation of claim 1, wherein the unitform is adapted for oral administration.
 3. The pharmaceuticalpreparation of claim 2, wherein the form adapted for oral administrationis a tablet.